1. Field of the Invention
This invention relates to a thermal processing jig for thermally processing a workpiece placed on a top surface thereof. More particularly, this invention is used as a jig for connecting plural members by brazing or the like, in which the plural members are connected by disposing brazing material at connecting portions between the plural members serving as a workpiece; then by mounting the workpiece applied with the brazing material on a top surface of the jig, then by placing the workpiece into a high temperature furnace, and then by melting the brazing material. This invention is also used as a jig for thermally processing plural workpieces coated with surface treatment material, e.g., thermosetting coating, in which the workpieces are thermally processed by mounting the workpieces on a top surface of the jig, and then by disposing the workpieces for a prescribed period into a high temperature furnace for heating the workpieces to a prescribed temperature.
2. Description of Related Art
In a conventional thermal processing jig, for example, a jig 20 shown in FIG. 4 including an outer peripheral frame 21 for structuring the jig 20, a mounting portion 22 for mounting a workpiece thereon, and a stay 24 is formed rigidly by employing thick members and by fixedly connecting the members with welds 23. In a case where the jig 20 having a workpiece mounted thereon is placed into a furnace, high-temperature heat causes thermal stress upon the jig 20, and often results in deformation of the jig 20. Therefore, in order to prevent deformation of the thermal processing jig, thick members are used for forming the jig rigidly.
Since the members of the rigidly formed jig are heated up from a cold state in a frequent and repetitive manner, then exposed to a high temperature atmosphere of 1100xc2x0 C. or more inside a furnace, and then cooled to a cold state, the members are subject to considerable deformation caused by welding stress in a manufacturing process and internal stress from the property of the material due to heat difference between the heating process and the cooling process. In association with the deformation of the members, the workpiece mounted on the top surface of the mounting portion will also deform. Accordingly, a subsequent process of inspecting all products and an additional process of relieving the stress are necessary for products requiring accurate dimensional tolerance.
Forming the thick and rigid jig causes the jig to become heavy. Therefore, the weight of the jig itself will take up a large portion of the entire weight in processing with the furnace. That is, absorption of thermal energy by the jig has no significance from an aspect of heating energy. Most preferably, heating energy should only be applied upon the workpiece disposed inside the furnace. However, in reality, a considerable amount of heat is absorbed by the conventional rigid jig in a case where the jig and the workpiece are placed in a same atmosphere of high temperature. Therefore, a large space for a heating zone of the furnace and a long time for the heating process are required for the conventional jig. At the same time, since the jig has large thermal capacity, the jig is difficult to cool into a cold state. Therefore, a large space for a cooling zone when using a continuous thermal processing furnace and a long time for a cooling process are required for the jig. Repetitively using the jig for a numerous amount of times causes considerable thermal stress and results to considerable deformation, even to the rigidly formed jig. The thermally deformed jigs were disposed of since the jigs were difficult to be reused. Not only is the jig used for a short period, but is also unable to use thermal energy efficiently due to the large amount of heat absorption of the jig. Therefore, a large sized furnace and high running cost was necessary for the conventional jig.
It is an object this invention to solve the foregoing problems by providing a jig causing no or hardly any deformation from thermal stress upon the jig in a case where the jig is disposed into a thermal furnace along with a workpiece, thereby allowing the jig to be used for a period considerably longer than the conventional jig. By forming a thin and light-weight jig, the productivity for the operator can be increased, the amount of heat absorption of the jig placed inside a furnace can be reduced to enable a more efficient thermal processing of a workpiece, and the apparatus for thermal processing can be size-reduced to enable reduction in initial cost and running cost.
This invention provides a thermal processing jig for a workpiece including: an outer peripheral frame formed of a plurality of members; and a mounting portion arranged within the outer peripheral frame for mounting the workpiece, wherein the outer peripheral frame and the mounting portion are movably connected, wherein the plurality of members forming the outer peripheral frame are connected via an expansion space capable of absorbing expansion caused during thermal expansion of the outer peripheral frame and the mounting portion, and wherein the plurality of members forming the outer peripheral frame and a member constituting the mounting portion are connected via the expansion space.
This invention can also provide a thermal processing jig for a workpiece, wherein the outer peripheral frame and the mounting portion are movably connected by piercingly forming an insertion aperture at a connecting portion between the outer peripheral frame and the mounting portion, and by inserting the connection axis through the insertion aperture, for enabling each member of the outer peripheral frame and the mounting portion to move at the connection portion during thermal expansion of the outer peripheral frame and the mounting portion, wherein the insertion aperture is formed for inserting the connection axis therethrough, and wherein the connection axis has a diameter smaller than the insertion aperture.
This invention can also provide a thermal processing jig for a workpiece, wherein the plurality of members forming the outer peripheral frame are directly connected to each other, and wherein the plurality of members forming the outer peripheral frame and the mounting portion are directly connected.
This invention can also provide a thermal processing jig for a workpiece, wherein the plurality of members forming the outer peripheral frame are connected to each other via an intermediary attachment member, and wherein the plurality of members forming the outer peripheral frame and the mounting portion are connected via the intermediary member.
This invention can also provide a thermal processing jig for a workpiece, wherein the connection axis is removably connected to the insertion aperture.
This invention can also provide a thermal processing jig for a workpiece, wherein the connection axis is unremovably connected to the insertion aperture.
This invention can also provide a thermal processing jig for a workpiece, wherein the mounting portion is formed with a plurality of members.
This invention can also provide a thermal processing jig for a workpiece, wherein the mounting portion is formed from a single connected member or a single united bodied member.
With this invention, a workpiece targeted for thermal processing is mounted on a top surface of a mounting portion of a jig, and the jig having the workpiece mounted thereon is disposed into a thermal furnace. The workpiece is heated inside the thermal furnace and thermally processed, e.g., brazed, while the thermal energy is inevitably absorbed by the jig. The heating cause thermal expansion upon the members forming the jig. Despite the thermal expansion caused upon the members, each member is movably connected; furthermore, expansion spaces for absorbing the expansion of the members are formed between the members of the outer peripheral frame and also between the outer peripheral frame and the mounting portion.
The expansion spaces formed between the members therefore absorbs the expansion from the thermally expanded members, as opposed to a conventional example where members of a jig such as an outer peripheral frame and a mounting portion for mounting a workpiece are firmly connected by welding or the like. Each member, along with the expansion absorption of the expansion spaces, can absorb the stress created in association with the thermal expansion since each member is movably connected. Accordingly, the expansion spaces can therefore absorb the expansion, from the thermally expanded members, as opposed to a conventional example where members of a jig such as an outer peripheral frame and a mounting portion for mounting a workpiece are firmly connected by welding or the like.
Stress and deformation upon the jig as well as deformation of the workpiece from the stress of the jig can be prevented since the members are able to absorb the thermal expansion. Since deformation and thermal stress upon the jig can be prevented, the jig is not required to be formed rigidly, but is instead able to be formed only with strength sufficient for handling or mounting the workpiece. Accordingly, the members of the jig can be formed with a thin thickness, so that the thermal energy absorbed by the jig can be absorbed to an amount considerably less than that of the conventional jig. Accordingly, unnecessary absorption of thermal energy can be prevented and thermal processing of the workpiece can be provided efficiently. Consequently, the space for a heating zone inside a furnace and the time for heating can be reduced. At the same time, the jig having little thermal capacity is easy to cool into a cold state, thereby requiring less space for a cooling zone than the conventional jig in a case where a continuous thermal processing furnace is used and also requiring less time for a cooling process.
Each member is movably connected via an expansion space. In movably connecting the members, an insertion aperture is piercingly formed at a connecting portion of each member for inserting therethrough a connection axis, in which the connection axis having a smaller diameter than the insertion aperture is pierced therethrough. Forming the connection axis with a smaller diameter than the insertion aperture allows a play portion to be created in the insertion aperture. The play portion enables the members to move in association with the thermal expansion of the members.
Although the members of the jig include plural members forming the outer peripheral frame and the mounting portion arranged inside the outer peripheral frame for mounting the workpiece, the members can be directly connected via the insertion aperture and the connection axis, or connected via an intermediary attachment member. By connecting the members via the intermediary attachment member, the forming of the members of the jig can be simplified, thereby providing productivity and versatility for the jig.
In connecting the members directly, the members of the jig will be subject to a process such as bending. Therefore, direct connection of the members has a drawback of requiring more labor in processing the members of the jig. Nevertheless, direct connection of the members can simplify manufacture of the jig since no intermediary attachment member is required. Therefore, connection of the members can be determined according to the purpose for processing the workpiece. By forming the connection axis in a removable manner with respect to the insertion aperture, the connection axis can be removed from the members for allowing the members to be modified by pressing or the like. For example, a jig deformed into a wound state can be flattened and reused as a thermal processing jig. As opposed to the conventional jig, the jig of this invention will rarely be required to be discarded.
A considerable amount of thermal expansion can be absorbed even for a large sized mounting portion and thermal stress can be prevented by forming the mounting portion with plural members connected movably via the expansion space.
In a case where the jig is of a small size area, the mounting portion can also be formed from a single connected or united bodied member since the amount of thermal expansion is small and the expansion space formed between the mounting portion and the outer peripheral frame will be able to absorb the thermal expansion, thereby forming the jig with a simple structure and enabling manufacture of an inexpensive product.